If you have read the ArsTechnica review, he explicitly states that the mouse itself does not have a speaker that actually produces the sound. The click is performed by the rocking mechanism that is the exact same as for the normal Apple Pro mouse.

I think I'll try out the mouse at the Apple store later this month, but I'm never going to buy another chorded mouse. With BT eventually on all of my machines, I'll just use a BT KBM and skip the cords. I don't really mind batteries that much.